Method for regulating rheological property of shield fine sand mortar by using functional polycarboxylate superplasticizer

Abstract

This invention relates to the field of tunnel engineering materials technology, and in particular to a method for regulating the rheological properties of shield tunneling fine sand mortar using functional polycarboxylate superplasticizers. The method includes: providing cement, shield tunneling fine sand, natural sand, water, and functional polycarboxylate superplasticizers; the functional polycarboxylate superplasticizers include anti-mud adsorption type polycarboxylate superplasticizers and ultra-dispersed viscosity-reducing type polycarboxylate superplasticizers; setting the target flowability and target plastic viscosity of the cement mortar; based on a preset water-reducing equivalent complementary relationship model and a plastic viscosity regulation relationship model, using the set target flowability to match the water-reducing equivalent complementary relationship as a constraint condition, simultaneously solving to determine the dosage of PCE-SP and PCE-VR; by establishing a quantitative correlation between the fine aggregate coupling parameter D / PFT and the mortar yield stress and residual viscosity, the rheological properties of the mortar can be accurately predicted and targeted, significantly simplifying the mortar mix design process and reducing R&D and engineering application costs.

Description

Technical Field

[0001] This invention relates to the field of tunnel engineering materials technology, and in particular to a method for regulating the rheological properties of shield tunneling fine sand mortar using functional polycarboxylate superplasticizers. Background Technology

[0002] With the rapid development of underground space development, shield tunneling has generated a large amount of shield sand and slag with high mud content and high fine powder content. Replacing natural sand with this slag to prepare cement-based mortar is the core way to realize the green resource utilization of this type of solid waste. Polycarboxylate superplasticizer (PCE) is a key material for regulating the workability and rheological properties of this type of mortar.

[0003] In existing technologies, various functional polycarboxylate superplasticizers have been developed for different application scenarios, among which two core products are the most widely used: One type is the anti-mud adsorption polycarboxylate superplasticizer (PCE-SP). PCE-SP is mostly prepared through molecular structure modification. It typically involves moderately crosslinking conventional comb-type polycarboxylate superplasticizers with bridging monomers at both ends that have polymerization activity, forming a fragmented network structure, or optimizing the molecular structure by introducing cationic adsorption groups. Its core function is to prevent side chains from embedding into the interlayer structure of clay minerals by increasing the molecular size, or to preferentially adsorb and shield clay active sites, thereby reducing the ineffective adsorption of superplasticizers in clay minerals. This solves the problem of rapid increase in superplasticizer dosage and rapid performance loss over time in high-mud-content aggregate systems. Current technologies mostly apply it to ordinary concrete systems with high-mud-content sand and gravel aggregates.

[0004] The second type is ultra-dispersed viscosity-reducing polycarboxylate superplasticizer (PCE-VR). PCE-VR achieves structural modification by optimizing the density of adsorption groups in the main molecular chain and adjusting the length and distribution of side chains. It can significantly enhance the adsorption capacity and steric hindrance effect of molecules on the surface of fine powder particles. Its core function is to quickly disperse the flocculated structure of cement and fine powder particles, reduce the internal friction resistance between particles, thereby significantly reducing the plastic viscosity of cement-based systems and improving pumping performance. Existing technologies often apply it to systems with low water-cement ratio and high fine powder content, such as high-strength concrete with manufactured sand and self-compacting concrete.

[0005] However, in the actual engineering application of shield tunneling fine sand mortar, there is a great challenge in accurately controlling the dosage of these two types of water-reducing agents: (1) Since the quantitative mathematical relationship between the dosage of the two types of water-reducing agents and the core performance of mortar has not been established, it is impossible to simultaneously meet the dual requirements of target fluidity and target plastic viscosity. It is often necessary to repeatedly test mixes to barely meet the construction requirements, resulting in extremely low design efficiency and the inability to obtain the optimal dosage ratio. (2) The dosage was not designed in conjunction with the core characteristics of the shield sand such as gradation and mud content. The same set of empirical proportions can only be adapted to a single working condition. When the quality and dosage of the shield sand change, the control effect is lost, and the rheological properties of the mortar cannot be stably controlled, which can easily lead to construction safety hazards such as pump blockage.

[0006] The information disclosed in this background section is intended only to enhance the understanding of the general background of this disclosure and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0007] This invention provides a method for regulating the rheological properties of shield tunneling fine sand mortar using a functional polycarboxylate superplasticizer, which can effectively solve the problems in the background art.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for regulating the rheological properties of shield tunneling fine sand mortar using functional polycarboxylate superplasticizers, the method comprising: S1 provides cement, shield tunneling powder, fine sand, natural sand, water, and functional polycarboxylate superplasticizers; the functional polycarboxylate superplasticizers include anti-mud adsorption polycarboxylate superplasticizer PCE-SP and ultra-dispersed viscosity-reducing polycarboxylate superplasticizer PCE-VR; S2 sets the target fluidity and target plastic viscosity of the cement mortar. ; S3, based on the preset water reduction equivalent complementary relationship model and plastic viscosity control relationship model, matches the water reduction equivalent complementary relationship with the target flowability set in step 2, and... As constraints, solve the simultaneous equations to determine the PCE-SP doping level C. SP The doping C of PCE-VR VR ; S4 Weigh PCE-SP and PCE-VR according to the dosage in step S3, and mix them with the remaining raw materials to prepare cement mortar that meets the target rheological properties.

[0009] This invention addresses the challenges of controlling the rheological properties of shield tunneling mortar due to its high mud and fine powder content, resulting in low water-reducing agent dispersion efficiency and inaccurate control of the coupling between fluidity and viscosity. It employs the synergistic effect of two functional polycarboxylate water-reducing agents: an anti-mud adsorption type and a super-dispersed viscosity-reducing type. By simultaneously solving a complementary relationship model of water-reducing equivalent and a plastic viscosity control model, precise control of the two core rheological parameters—mortar fluidity and plastic viscosity—is achieved. Compared to the traditional empirical mix design method of repeated trial mixing, this invention upgrades rheological property control from a trial-and-error mode to a quantitative calculation mode. It can accurately determine the optimal dosage of the two water-reducing agents in one step, eliminating the need for multiple adjustments and improving mix design efficiency. Simultaneously, it ensures that the rheological properties of the shield tunneling mortar perfectly match the engineering construction requirements, realizing the high-value resource utilization of shield tunneling excavation waste and reducing the project's dependence on natural sand.

[0010] Preferably, the target flowability is 250±5mm. On the one hand, this range is highly consistent with the mainstream workability requirements of mortar pumping and self-compacting construction in shield tunneling projects. Within this flowability range, the mortar has both good fluidity and anti-segregation performance, and will not have problems such as bleeding, stratification, or clumping. On the other hand, within this flowability range, the mortar is in a stable and fully plastic flow state, which can eliminate the interference of yield stress abrupt change and thixotropic effect on the test results. This allows the linear fitting correlation coefficient between the fine aggregate property coupling parameter D / PFT and the mortar yield stress and residual viscosity to stably reach above 0.95, which greatly improves the prediction accuracy of the subsequent rheological parameter correlation model. It avoids the prediction deviation caused by nonlinear fluctuations in rheological parameters and aggregate properties when the flowability deviates from this range, and provides a stable and unified benchmark condition for the accurate calibration and prediction of rheological parameters.

[0011] Preferably, the target plastic viscosity Determined by the requirements of engineering applications; for example, for pumping construction, The pressure is usually controlled within the range of 0.3~0.4 Pa·s; for self-compacting concrete, It is usually controlled within the range of 0.4~0.5 Pa·s.

[0012] Furthermore, the complementary relationship model for water reduction equivalents is as follows: α×C SP +β×C VR =W0; (1) Where α is the water reduction efficiency coefficient of PCE-SP, β is the water reduction efficiency coefficient of PCE-VR, and α > β; W0 is the total water reduction equivalent constant required for cement mortar to reach the target fluidity, which is determined by the type of cement and the amount of fine sand added to the shield tunnel.

[0013] More specifically, the core principle of the water-reducing equivalent complementary relationship model is: under the condition of fixed water-cement ratio and target fluidity, the total dispersion capacity required for cement mortar to reach the same initial spread is constant. This invention uses water-reducing equivalent W0 to characterize this total dispersion capacity. The dispersion capacity of the two functional water-reducing agents can be quantitatively complemented by the water-reducing efficiency coefficient. The experimental calibration method for generating the water reduction efficiency coefficients α and β and the total water reduction equivalent constant W0 is as follows: W1 uses the same type of cement as the target project, and the amount of fine sand and water-cement ratio of the shield tunneling powder are fixed as the design values ​​of the target project. The target fluidity is set as T0. W2 adjusts the PCE-SP doping level C without adding PCE-VR. SP The spread of cement mortar under different admixtures was measured, and C0 plotted. SP - The spread curve determines the minimum PCE-SP doping amount required to achieve the target spread value T0, denoted as C. SP 0 At this point, according to equation (1), we can obtain: W0 = α × C SP 0 ; W3 adjusts the PCE-VR doping level C without adding PCE-SP. VR The spread of cement mortar under different admixtures was measured, and the CVR-spread curve was plotted. The minimum PCE-VR admixture required to achieve the target spread value T0 was determined and denoted as C. VR 0 At this point, according to equation (1), we can obtain: W0 = β × C VR 0 ; Combining the above two equations, we can obtain α×C. SP 0 =β×C VR 0 By setting the water reduction efficiency coefficient α=1.0 of PCE-SP as the benchmark value, β=C can be calculated. SP 0 / C VR 0 At the same time, determine W0=C SP 0 Alternatively, the values ​​of α, β, and W0 can be optimized to suit engineering scenarios by calibrating parameters through multiple sets of compound tests.

[0014] The water-reducing equivalent complementary relationship model proposed in this invention solves the problems of inability to quantify the dispersion ability and large fluctuations in fluidity after compounding when two polycarboxylate superplasticizers with different functions are compounded. The water-reducing equivalent complementary relationship model standardizes and quantifies the dispersion ability of the two superplasticizers through the water-reducing efficiency coefficient. With the total water-reducing equivalent W0 as a constant benchmark, it realizes the complementary conversion of the dosage of the two superplasticizers under a fixed target fluidity, breaking the problem that the replacement of superplasticizer types inevitably leads to fluidity fluctuations in the traditional compounding process. At the same time, the parameter calibration method provided by this invention uses raw materials and mix proportion parameters that are completely consistent with the target project, ensuring the engineering adaptability of the calibration parameters. By setting the benchmark value of α=1.0, parameter calibration can be quickly completed with only two sets of single-component tests. It can also be further calibrated and optimized through multiple sets of compounding tests, taking into account the dual needs of rapid application in engineering field and high-precision calibration in laboratory, greatly reducing the workload of mix proportion trial mixing and shortening the mix proportion design cycle before construction.

[0015] Furthermore, the plastic viscosity regulation relationship model is as follows: (2) in, The plastic viscosity of cement mortar. , is the reference plastic viscosity of cement mortar when the target fluidity is achieved using only PCE-SP as a functional polycarboxylate superplasticizer; k is the viscosity reduction coefficient, which is determined by the amount of fine sand admixture and fine powder content in the shield tunneling powder. The fine powder content is the percentage of particles with a diameter ≤0.15mm in the shield tunneling powder to the total mass of the shield tunneling powder.

[0016] More specifically, the principle of the plastic viscosity control model is as follows: Under the condition of maintaining the initial fluidity of mortar, the plastic viscosity of the system mainly depends on the mass proportion of the viscosity-reducing component PCE-VR in the total water-reducing agent, rather than its absolute dosage. By adjusting the proportion of PCE-VR, the plastic viscosity of the mortar can be precisely linearly controlled. The plastic viscosity control model realizes the decoupled control of mortar fluidity and plastic viscosity, solving the problem in the existing technology that adjusting the dosage of water-reducing agent will inevitably change both fluidity and viscosity at the same time, and it is impossible to control the viscosity alone under the premise of fixed fluidity. The plastic viscosity control relationship reveals the core law that under the conditions of constant total water-reducing equivalent and constant target fluidity, the plastic viscosity of mortar and the mass proportion of the viscosity-reducing water-reducing agent PCE-VR in the total water-reducing agent are precisely linearly negatively correlated. Without changing the core mix proportion parameters such as water-cement ratio and aggregate gradation, the plastic viscosity of mortar can be linearly and precisely controlled simply by adjusting the compounding ratio of the two water-reducing agents.

[0017] Preferably, The determination method is as follows: Prepare a reference mortar according to the target engineering mix proportion, without adding PCE-VR, and determine the PCE-SP dosage C required to make the initial spread of the mortar reach the target flowability through experiments. SP 0 The rheological curve of the reference mortar was tested using a rheometer, and the rheological curve was fitted using the Herschel-Bulkley model with a shear rate of 50 s⁻¹. -1 The apparent viscosity below is taken as the plastic viscosity, and this value is recorded as . ; Preferably, k is determined as follows: k is the decrease in plastic viscosity caused by a unit change in the PCE-VR ratio, characterizing the viscosity-reducing efficiency of PCE-VR; it can be simplified by a two-point method: select two mixing points, 0% and 50% of PCE-VR ratio, and measure the plastic viscosity of the two groups of mortars respectively while maintaining the target flowability. and Through formula The k value can be calculated; alternatively, multiple experimental groups with different PCE-VR ratios can be set up, and a more accurate k value can be obtained through linear regression fitting.

[0018] Furthermore, in step S3, the complementary relationship model of water reduction equivalent and the plastic viscosity regulation relationship model are combined to... Solving equations (1) and (2) for the constraints, we obtain C. SP and C VR .

[0019] This invention utilizes a simultaneous water-reducing equivalent complementary relationship model and a plastic viscosity control relationship model. By matching the target flowability with the water-reducing equivalent complementary relationship and using the target plastic viscosity as a constraint, a system of two linear equations can be solved in one go. This allows for the precise calculation of the optimal dosage of PCE-SP and PCE-VR, achieving simultaneous and precise control of mortar flowability and plastic viscosity. Compared to traditional methods that require fixing the flowability first and then repeatedly adjusting the viscosity through multiple rounds of trial mixing, this invention eliminates the need for repeated adjustments, improving mix design efficiency by over 80%. Furthermore, the solution process can be automated using Excel spreadsheets and simple mini-programs, eliminating the need for specialized numerical calculation software and complex professional knowledge. On-site technicians can quickly learn to operate this method, solving the problems of existing rheological control methods being complex to operate, requiring high levels of professional expertise, and difficult to scale up and apply on-site.

[0020] Furthermore, the method also includes: establishing a correlation model between the fine aggregate property coupling parameter D / PFT and the mortar rheological parameters, predicting the range of rheological parameters for a given shield tunneling fine sand content based on the correlation model, and adjusting the mortar rheological parameters based on the range of rheological parameters. .

[0021] Furthermore, the formula for calculating D / PFT is: ; Among them, D s Where is the equivalent diameter of the mixed fine aggregate, and SSA is the specific surface area of ​​the mixed fine aggregate. This refers to the volume fraction of the mixed fine aggregate. The filling coefficient is the mixed fine aggregate, which is shield tunneling fine sand and natural sand; Mortar rheological parameters include yield stress and residual viscosity; The correlation model is a linear regression model, and its expression is: ; ; Where a, b, c, and d are linear regression coefficients. For yield stress, This refers to the residual viscosity.

[0022] More specifically, the process of establishing the association model is as follows: Q1 uses the fixed water-cement ratio and mortar ratio as the baseline values, and sets the dosage gradient of shield tunnel fine sand of 0%, 5%, 10%, 20%, and 30% to replace natural sand. By adjusting the dosage of water-reducing agent, the initial spread of each group of mortar is kept constant, eliminating the interference of fluidity differences on the test results. Q2 used a rheometer to test the rheological curves of each group of mortars, and obtained the yield stress of each group of mortars by fitting the Herschel-Bulkley model. and residual viscosity ; Q3. Determine the filling coefficient of each group of mixed fine aggregates. Equivalent diameter D s Specific surface area (SSA) is substituted into the D / PFT calculation formula to obtain the corresponding D / PFT values ​​for each group. Q4. A scatter plot was drawn with D / PFT as the x-axis and rheological parameters as the y-axis, and the result was obtained through linear regression fitting. , By establishing the linear equation with D / PFT, the regression coefficients a, b, c, and d are determined, and the correlation model is completed.

[0023] The specific steps for predicting the range of rheological parameters are as follows: After determining the target fine sand content of the shield tunneling material, measure the properties of the mixed fine aggregate at that content. D s And SSA, calculate the D / PFT value, and substitute it into the correlation model to get and The predicted value; the standard deviation of the regression analysis residuals is taken. , with predicted value The prediction range for rheological parameters can be determined as a 95% confidence interval, or by setting a fluctuation coefficient of ±5% to ±10% based on engineering experience.

[0024] Furthermore, The adjustment method is as follows: (1) If the predicted rheological parameter range meets the engineering requirements, add PCE-SP and PCE-VR according to step S3; (2) If the predicted mortar rheological parameters exceed the engineering requirements, the following adjustments shall be made: Decrease Using the numerical value as a constraint, solve equations (1) and (2) to obtain the new C. SP and C VR .

[0025] Furthermore, the shield tunneling fine sand is fine sand with a particle size ≤0.6mm obtained after separating and treating the slag from the slurry shield tunneling, and its mud content is 20~30%.

[0026] Furthermore, the shield tunneling fine sand is incorporated in a manner that replaces natural sand by an equal mass, with a substitution amount of 5-30%.

[0027] More specifically, the low admixture range of 5-10% can be used in main structural engineering projects with high requirements for the mechanical properties and durability of mortar, achieving stable disposal of shield tunneling excavation without affecting the core performance of the mortar; the high admixture range of 20-30% can be used in engineering scenarios such as grouting behind shield tunnel segments, cushion mortar, and temporary support mortar, significantly increasing the scale of shield tunneling excavation disposal.

[0028] Furthermore, before mixing the raw materials, an adsorption sacrificial agent is added to the raw materials. The adsorption sacrificial agent is preferentially adsorbed by clay minerals over functional polycarboxylate superplasticizers. The adsorption sacrificial agent is a compound of polyquaternary ammonium salt cationic polymer and small molecule phosphate anionic polymer.

[0029] By adding an adsorbent sacrificial agent before raw material mixing, a synergistic anti-mud system is formed with two functional polycarboxylate superplasticizers, further improving the rheological stability and effective utilization rate of high-mud-content shield tunnel fine sand mortar. Among them, the polyquaternary ammonium salt cationic polymer can preferentially adsorb onto the negatively charged clay mineral layers through electrostatic interaction, preventing the polyether side chains of the polycarboxylate superplasticizer from inserting into the clay lattice and avoiding ineffective adsorption of the superplasticizer by the clay. The small molecule phosphate anionic polymer can chelate and complex the polyvalent metal cations dissolved from the clay, inhibiting the flocculation effect of metal cations on the polycarboxylate superplasticizer, while dispersing clay agglomerates and reducing the internal friction resistance of the mortar. The synergistic effect of the two can improve the effective utilization rate of polycarboxylate superplasticizer, and ensure long-term stable rheological properties, making it perfectly adaptable to complex engineering scenarios such as long-distance pumping and high-temperature construction.

[0030] The technical solution of this invention can achieve the following technical effects: (1) This invention significantly reduces the ineffective adsorption of water-reducing agents on clay minerals through the synergistic application of anti-mud adsorption type PCE-SP and ultra-dispersed viscosity-reducing type PCE-VR. Experimental data show that the equilibrium adsorption capacity of PCE-SP on fine powder particles is only 18.9 mg / g, while that of conventional polycarboxylate water-reducing agents is as high as 62.3 mg / g, with an adsorption capacity reduction of about 70%, which greatly improves the utilization efficiency of water-reducing agents and reduces the cost of engineering materials; (2) This invention can precisely adjust the proportion of PCE-VR in the total water-reducing agent through the plastic viscosity control relationship model, thereby achieving linear control of the plastic viscosity of mortar. It effectively solves the problem of high viscosity and shear thickening caused by high dosage of shield sand, avoids the risk of pipe blockage during pumping construction, and improves construction safety and convenience. (3) This invention constructs a linear correlation model between the fine aggregate characteristic coupling parameter D / PFT and the mortar rheological parameter, which can realize the early prediction of the mortar rheological properties under different shield sand admixtures; at the same time, it also proposes a dual mathematical model of the complementary relationship of water-reducing equivalent and the plastic viscosity control relationship of two functional water-reducing agents, realizing the admixture admixture dosage from empirical trial mixing to quantitative calculation, improving the efficiency of mix design, with strong universality, and can be adapted to shield fine sand application scenarios with different quality and different admixtures; (4) This invention enables shield sand with high mud content and high fine powder content to be safely and stably applied to cement mortar at a dosage of 5-30%. The mortar with 30% shield sand controlled by this invention can achieve a level similar to the benchmark mortar in terms of workability, mechanical properties and volume stability, thus realizing the high-value-added green resource utilization of shield slag. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 A schematic diagram of the process for regulating the rheological properties of shield tunneling fine sand mortar using functional polycarboxylate superplasticizers; Figure 2 The effect curve of 30% shield sand on the plastic viscosity of cement mortar; Figure 3 This is a graph showing the relationship between the fine aggregate coupling parameter D / PFT and the mortar rheological parameters in Embodiment 2 of the present invention. Detailed Implementation

[0033] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0035] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application.

[0036] Example 1: Characterization and control of mortar rheological properties under different shield tunneling sand admixtures (1) Experimental raw materials: Cement: Onoda P・Ⅱ 52.5 type Portland cement; Natural sand: River sand with a fineness modulus of 2.9; Shield tunneling fine sand (SS): Fine sand obtained from the slurry shield tunneling debris of a certain river-crossing tunnel after separation and processing. The particle size is ≤0.6mm, the mud content is 26.7%, and the main mineral composition is quartz, feldspar, mica, a small amount of montmorillonite and kaolin. Functional polycarboxylate superplasticizers: PCE-SP (anti-mud adsorption type) and PCE-VR (super-dispersed viscosity reducing type), both with a mother liquor solid content of 50%.

[0037] (2) Experimental formulation and testing methods With a fixed water-cement ratio of 0.4 and a mortar-cement ratio of 0.5, five groups of cement mortar specimens were designed by replacing natural sand with shield tunneling fine sand at proportions of 0%, 5%, 10%, 20%, and 30% by mass. By adjusting the dosage of PCE-SP, the initial spread of each group of mortar was controlled within the range of 255±5mm (i.e., the target flowability range of 250±5mm) using a truncated cone mold test. The minimum dosage of PCE-SP required for each group to achieve the target flowability was recorded. The rheological curves of each group of mortars were tested using an R / S soft-solid rheometer equipped with a V40-20 rotor, following a preset stepped-rate-increasing shear program. The Herschel-Bulkley model was used. The obtained rheological curves were fitted to obtain the yield stress of each group of mortars. Key rheological parameters such as rheological index n; (3) Experimental results and analysis The variation of cement mortar fluidity with PCE-SP admixture under different shield sand admixtures is as follows: Figure 1 As shown, Figure 1 middle: 100%NS: The benchmark control group with 0% fine sand content in shield tunneling powder and all natural sand; 5%SS+95%NS: Test group in which shield tunneling powder and fine sand were used to replace 5% natural sand; 10%SS+90%NS: Test group in which shield tunneling powder and fine sand of equal quality replace 10% natural sand; 20%SS+80%NS: Test group in which shield tunneling powder and fine sand were used to replace 20% of natural sand; 30%SS+70%NS: Test group in which shield tunneling powder and fine sand were used to replace 30% of natural sand; Among them, NS represents natural sand and SS represents shield tunneling fine sand; Depend on Figure 1 It can be seen that PCE-SP can significantly improve the flowability of mortar, and the mortar flowability shows a stable increasing trend with the increase of PCE-SP dosage. At the same time, the incorporation of shield tunneling fine sand significantly increases the amount of water-reducing agent required to achieve the target flowability. When the flowability is stably controlled at 255±5mm, the admixture dosage of the 5%, 10%, 20%, and 30% shield tunneling sand dosage groups increased by 15.8%, 26.3%, 52.6%, and 84.2% respectively compared with the 0% baseline group. The core reason is that the number of fine particles in the shield tunneling fine sand increases significantly, which greatly increases the specific surface area and water demand of the solid particles in the cement mortar system, thereby increasing the demand for water-reducing agent. Rheological performance test results show that the rheological index n < 1 for the 0% baseline mortar without shield sand, exhibiting shear thinning characteristics; while after adding shield sand powder, the rheological index n of all mortar groups is > 1, showing significant shear thickening behavior, and the degree of shear thickening intensifies with the increase of shield sand content; at the same time, under the condition of controlling the spread at the same level, the mortar yield stress The rheological properties of the mortar increased significantly with the increase of the amount of shield sand. The above results indicate that the addition of shield fine sand significantly deteriorated the rheological properties of the mortar, verifying the necessity of rheological control.

[0038] Example 2: Rheological performance prediction and control based on D / PFT parameter coupling Based on Example 1, this embodiment establishes a correlation model between the fine aggregate property coupling parameter D / PFT and the mortar rheological parameters to achieve early prediction and directional control of rheological properties. (1) Parameter measurement and calculation Aggregate property parameter determination: The filling coefficient of the mixed fine aggregate under different shield sand admixtures in Example 1 was determined by the wet filling method. The particle size distribution of each group of mixed fine aggregates was obtained using a laser particle size analyzer, and the equivalent diameter D of the mixed fine aggregates was calculated using the corresponding formula. s and specific surface area (SSA); Coupling parameter D / PFT calculation: Substitute the measured parameters into the D / PFT calculation formula to calculate the corresponding coupling parameter values ​​for each group. The D / PFT calculation formula is as follows: ; In the formula, D s Where is the equivalent diameter of the mixed fine aggregate, and SSA is the specific surface area of ​​the mixed fine aggregate. This refers to the volume fraction of the mixed fine aggregate. The filler coefficient for the mixed fine aggregate; (2) Establishment of the association model right Figure 1 Five groups of mortar were tested for yield stress using a rheometer. and residual viscosity Simultaneously, the filling coefficient of each group of aggregates was determined. Equivalent diameter D s Specific surface area (SSA), calculate D / PFT value; plot D / PFT as the x-axis, and Plotting the D / PFT on the ordinate, the relationship between the D / PFT and rheological properties is as follows: Figure 2 As shown; Depend on Figure 2 It can be seen that the D / PFT value has a good linear positive correlation with the yield stress and residual viscosity of the mortar. The linear equation of the correlation model obtained by linear regression fitting is as follows: ; ; In the formula, a, b, c, and d are linear regression coefficients. After fitting verification, the linear fitting correlation coefficient of this model can stably reach above 0.95, which has extremely high prediction accuracy.

[0039] The correlation model established in this embodiment can achieve both positive prediction and negative regulation: Positive prediction: After determining the target fine sand content for the shield tunneling machine, measure the D of the mixed fine aggregate at that content. s SSA and The D / PFT value is calculated and then substituted into the above correlation model to obtain the result. and The predicted value; the standard deviation of the regression analysis residuals is taken. , with predicted value The prediction range of rheological parameters can be determined as a 95% confidence interval, or by setting a fluctuation coefficient of ±5% to ±10% based on engineering experience. Reverse control: When the project plans to use 20% shield tunneling fine sand admixture, first calculate the D / PFT value under this admixture, and predict the yield stress and residual viscosity range of the mortar through the correlation model; if the predicted viscosity exceeds the acceptable range of the project, then increase the dosage of the viscosity-reducing component PCE-VR in subsequent control, and adjust the target plastic viscosity based on the prediction results. This provides a benchmark for subsequent coordinated regulation using the dual-model approach.

[0040] Example 3: Coordinated Regulation of PCE-SP and PCE-VR Based on Mathematical Model (1) Engineering conditions and parameter calibration A shield tunneling project across a river requires the use of cement mortar mixed with 30% shield tunneling powder and fine sand, with a target initial spread of 250±5mm. Pumping construction requires a target plastic viscosity. .

[0041] Through preliminary standardized testing and calibration, the model parameters suitable for the raw materials and mix proportions of this project are as follows: Water reduction efficiency coefficients: α = 1.2, β = 0.8; Total water reduction equivalent constant: W0 is 2.4; Reference plastic viscosity: It is 0.45 Pa·s; Viscosity reduction coefficient: k is 0.15 Pa·s; (2) The control steps are as follows: (21) The complementary relationship model of water reduction equivalent is as follows: 1.2×C SP +0.8×C VR =2.4; (22) Substitute into the plastic viscosity control relationship model, with As constrained, we obtain: (23) Solving the above two equations simultaneously, we find that the mass percentage of PCE-VR in the total water-reducing agent should not be less than 66.7%; (24) To meet the engineering requirements, the PCE-VR ratio is set at 66.7%, i.e., C VR =2C SP Substituting into the water reduction equivalent formula, we get C. VR =1.714%, C Sp =0.857%.

[0042] (25) Calculated value of plastic viscosity at this time: 0.45-0.15 0.667 = 0.35 Pa·s; (26) According to C Sp =0.86%, C VR =1.71% (by mass of gel material) of the additive is weighed and added to the mix proportion to prepare mortar.

[0043] (3) Mortar preparation and performance verification C obtained from the above calculation Sp =0.86%, C VR Two types of functional polycarboxylate superplasticizers were weighed at a dosage of 1.71% and mixed with cement, shield tunneling fine sand, natural sand, and water in the corresponding proportions for this project. Specimens were prepared using conventional cement mortar mixing technology.

[0044] Testing revealed that the initial spread of the prepared mortar was 252 mm, meeting the target flowability requirement of 250 ± 5 mm; the plastic viscosity of the mortar, measured using a rheometer, was 0.34 Pa·s, which meets the requirements. The pumping construction requirements are met, and the rheological index n < 1, completely eliminating the risk of shear thickening caused by the 30% shield sand content.

[0045] Example 4: Synergistic Regulation Effect of Adding Adsorption Sacrificial Agent Based on Example 3, this embodiment adds an adsorption sacrificial agent to further improve the utilization efficiency of the water-reducing agent. The specific scheme is as follows: Before mixing the mortar raw materials, add 0.2% (by mass percentage of cementitious material) of adsorbent sacrificial agent ASA300 to the mixing water. ASA300 is a compound of polyquaternary ammonium salt cationic polymer and small molecule phosphate anionic polymer. The remaining raw materials, mixing ratio, and target performance requirements are the same as in Example 3. Through testing, it was found that, while maintaining the performance requirements of initial mortar spread of 250±5mm and plastic viscosity ≤0.35Pa·s, the dosage of PCE-SP can be reduced to 0.7%, the dosage of PCE-VR can be reduced to 1.4%, and the total amount of admixtures is reduced by about 18% compared with Example 3.

[0046] The adsorption sacrificial agent can be preferentially adsorbed by clay minerals before functional polycarboxylate superplasticizers. Among them, the polyquaternary ammonium salt cationic polymer preferentially adsorbs into the negatively charged clay mineral interlayer through electrostatic interaction, preventing the side chains of the superplasticizer from inserting into the clay lattice. The small molecule phosphate anionic polymer can chelate the polyvalent metal cations dissolved from the clay, inhibiting their flocculation effect on the superplasticizer. The synergy of the two further reduces the ineffective adsorption of the superplasticizer, improves the utilization efficiency of the superplasticizer, and reduces the cost of engineering materials. Example 5:

[0047] This embodiment, based on the raw materials in Example 1, with a fixed shield sand content of 30% and a target spread of 250±5mm, designs a series of compounding schemes with PCE-VR proportions ranging from 0% to 80%; the specific admixture content for each proportion is determined according to the water-reducing equivalent model, mortar is prepared and its plastic viscosity is measured, resulting in the following... Figure 3 Results shown: Figure 3 The meanings of the various legends in the figure are as follows: Depend on Figure 3 It can be seen that, under the condition of maintaining the target fluidity of mortar, the plastic viscosity of mortar shows a significant linear decreasing trend with the increase of the proportion of PCE-VR in the total water-reducing agent, which is in complete agreement with the plastic viscosity control relationship model proposed in this invention, verifying the accuracy and reliability of the model.

[0048] Comparative Example 1: In this comparative example, the conventional comb-type polycarboxylate superplasticizer PCE-OR was used instead of PCE-SP in Example 1. All other raw materials, mixing ratios, test conditions, and target flowability requirements were completely consistent with those in Example 1.

[0049] The test results show that when the content of shield sand exceeds 10%, the content of PCE-OR increases sharply compared with PCE-SP in order to maintain the target fluidity of 250±5mm. After 1 hour, the fluidity loss rate of mortar with 20% shield sand exceeds 60%, and the mortar with 30% shield sand completely loses its fluidity and cannot meet the engineering construction requirements. These results indicate that conventional polycarboxylate superplasticizers cannot effectively resist the ineffective adsorption of clay minerals in shield fine sand, have poor dispersion stability, and are not suitable for high mud content and high content shield sand mortar systems. This further verifies the technical advantages of the anti-mud adsorption type PCE-SP used in this invention.

[0050] Comparative Example 2: This comparative example operates under the same engineering conditions, raw materials, and target performance requirements as Example 3. However, it does not employ the dual mathematical model simultaneous solution method of this invention. Instead, it relies solely on engineering experience to repeatedly adjust the compounding ratio of PCE-SP and PCE-VR to achieve the target flowability and target plastic viscosity requirements.

[0051] The experimental results showed that the engineer in charge of the trial mixing barely achieved the target performance requirements after five consecutive trials, taking a total of 4 hours. Moreover, the final mixture ratio was not the optimal ratio, and the total amount of admixtures was 12% higher than that in Example 3. However, using the method of this invention, only one calculation is needed to obtain the accurate optimal ratio, improving the efficiency of mix design by more than 80% and significantly reducing material costs. This result verifies the quantitative mathematical model proposed in this invention, which can upgrade the rheological performance control from the traditional experience-based trial and error mode to a precise quantitative calculation mode, significantly improving the efficiency of mix design and engineering adaptability.

[0052] Table 1 is a data comparison table between the examples and comparative examples: Although this application has been described in conjunction with specific features and embodiments, it is obvious that various modifications and combinations can be made thereto without departing from the spirit and scope of this application. Accordingly, this specification and drawings are merely exemplary illustrations of the application as defined herein, and are to be considered as covering any and all modifications, variations, combinations, or equivalents within the scope of this application. Clearly, those skilled in the art can make various alterations and modifications to this application without departing from its scope. Thus, if such modifications and modifications fall within the scope of this application and its equivalents, this application intends to include such modifications and modifications.

Claims

1. A method for regulating the rheological properties of shield tunneling fine sand mortar using functional polycarboxylate superplasticizers, characterized in that, The method includes: S1 provides cement, shield tunneling powder, fine sand, natural sand, water, and functional polycarboxylate superplasticizers; the functional polycarboxylate superplasticizers include anti-mud adsorption type polycarboxylate superplasticizer PCE-SP and ultra-dispersed viscosity-reducing type polycarboxylate superplasticizer PCE-VR; S2 sets the target fluidity and target plastic viscosity of the cement mortar. ; S3, based on the preset water reduction equivalent complementary relationship model and plastic viscosity control relationship model, matches the water reduction equivalent complementary relationship with the target flowability set in step 2, and... As constraints, solve the simultaneous equations to determine the PCE-SP doping level C. SP and the doping C of PCE-VR VR ; S4 Weigh PCE-SP and PCE-VR according to the dosage in step S3, and mix them with the remaining raw materials to prepare cement mortar that meets the target rheological properties.

2. The method for regulating the rheological properties of shield tunneling fine sand mortar using functional polycarboxylate superplasticizers according to claim 1, characterized in that, The complementary relationship model for water reduction equivalents is as follows: α×C SP +β×C VR =W0;(1) Where α is the water reduction efficiency coefficient of PCE-SP, β is the water reduction efficiency coefficient of PCE-VR, and α > β; W0 is the total water reduction equivalent constant required for cement mortar to reach the target fluidity, which is determined by the type of cement and the amount of fine sand added to the shield tunnel.

3. The method for regulating the rheological properties of shield tunneling fine sand mortar using functional polycarboxylate superplasticizers according to claim 2, characterized in that, The plastic viscosity regulation relationship model is as follows: ； （2） in, The plastic viscosity of cement mortar. The reference plastic viscosity is the cement mortar that reaches the target fluidity when only PCE-SP is used as a functional polycarboxylate superplasticizer; k is the viscosity reduction coefficient, which is determined by the amount of fine sand in the shield tunneling powder and the fine powder content, wherein the fine powder content is the percentage of particles with a particle size ≤0.15mm in the shield tunneling powder to the total mass of the shield tunneling powder.

4. The method for regulating the rheological properties of shield tunneling fine sand mortar using functional polycarboxylate superplasticizers according to claim 3, characterized in that, In step S3, the water reduction equivalent complementary relationship model and the plastic viscosity regulation relationship model are combined to... Solving equations (1) and (2) for the constraints, we obtain C. SP and C VR .

5. The method for regulating the rheological properties of shield tunneling fine sand mortar using functional polycarboxylate superplasticizers according to claim 1, characterized in that, The method further includes: establishing a correlation model between the fine aggregate property coupling parameter D / PFT and the mortar rheological parameters, predicting the range of rheological parameters for a given shield tunneling fine sand content based on the correlation model, and adjusting the mortar rheological parameters based on the range of rheological parameters. .

6. The method for regulating the rheological properties of shield tunneling fine sand mortar using functional polycarboxylate superplasticizers according to claim 5, characterized in that, The formula for calculating the D / PFT is: ； Among them, D s Where is the equivalent diameter of the mixed fine aggregate, and SSA is the specific surface area of ​​the mixed fine aggregate. This refers to the volume fraction of the mixed fine aggregate. The filling coefficient is the mixed fine aggregate, which is shield tunneling fine sand and natural sand; The rheological parameters of the mortar include yield stress and residual viscosity; The correlation model is a linear regression model, and its expression is: ； ； Where a, b, c, and d are linear regression coefficients. For yield stress, This refers to the residual viscosity.

7. The method for regulating the rheological properties of shield tunneling fine sand mortar using a functional polycarboxylate superplasticizer according to claim 6, characterized in that, The The adjustment method is as follows: (1) If the predicted rheological parameter range meets the engineering requirements, add PCE-SP and PCE-VR according to step S3; (2) If the predicted mortar rheological parameters exceed the engineering requirements, the following adjustments shall be made: Decrease Using the numerical value as a constraint, solve equations (1) and (2) to obtain the new C. SP and C VR .

8. The method for regulating the rheological properties of shield tunneling fine sand mortar using functional polycarboxylate superplasticizer according to claim 1, characterized in that, The shield tunneling fine sand is fine sand with a particle size ≤0.6mm obtained after separation and treatment of slurry shield tunneling slag, and its mud content is 20~30%.

9. The method for regulating the rheological properties of shield tunneling fine sand mortar using a functional polycarboxylate superplasticizer according to claim 1, characterized in that, The shield tunneling fine sand is added in a manner that replaces natural sand by an equal mass, with a replacement amount of 5-30%.

10. The method for regulating the rheological properties of shield tunneling fine sand mortar using a functional polycarboxylate superplasticizer according to claim 1, characterized in that, Before mixing the raw materials, an adsorption sacrificial agent is added to the raw materials. The adsorption sacrificial agent is preferentially adsorbed by clay minerals than functional polycarboxylate superplasticizers. The adsorption sacrificial agent is a compound of polyquaternary ammonium salt cationic polymer and small molecule phosphate anionic polymer.

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